Simplify the following expression: $n = \dfrac{y}{5} + \dfrac{y}{7}$
Solution: In order to add expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $5$ and $7$ $\lcm(5, 7) = 35$ $ n = \dfrac{7}{7} \cdot \dfrac{y}{5} + \dfrac{5}{5} \cdot \dfrac{y}{7} $ $n = \dfrac{7y}{35} + \dfrac{5y}{35}$ $n = \dfrac{7y +5y}{35}$ $n = \dfrac{12y}{35}$